Free Subterrestrial by Michael McBride

stone ahead of them. They reminded him of tourists the way they looked everywhere but where they were going.
    “Over there is where the TBM first broke through,” Thyssen said. “You can tell by these erosion marks that there was approximately four feet of running water bisecting the cavern.”
    “What kind?” Calder asked.
    “Freshwater, we believe, although it’s impossible to tell for sure. The structural destabilization and sudden change in pressure were ultimately responsible for flooding the entire cavern with seawater. We’ve stabilized the fracture zone, but the water is still coming in as fast as we can pump it back out.”
    “Is this safe?” Nabahe asked. “I mean, what’s keeping this whole place from coming down on our heads?”
    Thyssen stopped and turned to face him.
    “I am,” he said in a voice that brooked no argument. Payton saw a hint of fire in the man’s expression that hadn’t been there before. It disappeared as quickly as it had appeared.
    Thyssen resumed walking and guided them into a much narrower section. The ceiling was significantly lower and piles of earth still remained, shoved aside just far enough to form a narrow passage through which they were forced to use their hands to climb. Payton’s helmet scraped the sandstone as he squeezed through and picked his way down the opposite side of the treacherous slope. Lengths of bent and sheared metal stood from the rocks. He wondered about their origin; surely they couldn’t have all come from the TBM. One piece almost looked like the propeller of a small plane.
    A bank of battery-powered lights had been erected in the middle of the narrow corridor and in such a way that they spotlighted both walls, revealing deep recesses in the rock. It wasn’t until he was nearly on top of the first one that he saw the dark shape crammed into the back. The brittle fur standing from the desiccated pelt. The blanched, partially articulated skeletal remains. And the malformed primate skull unlike any he had ever seen before.

IV
    Hart pushed past the others and stood in the mouth of the recess. She realized she wasn’t breathing and gasped for air. As though from somewhere far away, she watched her trembling hand reach inside and trace the contours of the skull.
    The facial architecture was strikingly similar to both bonobos and chimpanzees, at least from the maxillae down. The upper jaw featured large canine teeth and molars lacking the specialization of other apes and worn down by grinding, which suggested an omnivorous diet. The lower jaw was disarticulated and rested on its empty rib cage. The cranial vault was disproportionately large and oddly shaped. It was elongated and tapered to a blunted point, almost like a bike helmet, or the hominin remains discovered in Paracas, Peru.
    It was the orbital sockets that caught her attention. They were extraordinarily shallow, not nearly deep enough to accommodate even an average-size globe.
    “What is it?” she whispered.
    “We were hoping you might be able to tell us,” Thyssen said.
    Hart could only shake her head in disbelief as she scrutinized the remains.
    The rib cage was significantly less conical in shape than most primates’, which theoretically meant much shorter intestines in the abdomen and a diet consisting of a larger ratio of animal to plant matter. That theoretically fit with the larger brain, as digestion wouldn’t have monopolized the blood flow, freeing up more for the remainder of the body. The lordotic curvature of the cervical and lumbar spines, in conjunction with the broad iliac flare, wide acetabular distance, and ninety-degree pubic arch defined its posture as upright. The bowed formation of the knees and highly developed greater trochanters indicated primarily bipedal locomotion, which was confirmed by the relative length of the femurs to the humeri. There was even a slight arch in the feet, despite the valgus positioning of the great toe, which was utilized for grasping